Vesicles encapsulating useful substances in the internal aqueous phase and their dispersions are an important technology in various fields such as pharmaceuticals, perfumes, cosmetics and food stuffs. Examples of widely used lipids that constitute the membrane of the vesicle include mixed lipids prepared by mixing negativ ly charged phospholipids such as diacylphosphatidyl glycerol, diacylphosphatidyl inositol, diacylphosphatidyl serine with diacylphosphatidyl choline or a mixture of diacylphosphatidyl choline and cholesterol in an arbitrary proportion.
However, diacylphosphatidyl glycerol, diacylphosphatidyl inositol, diacylphosphatidyl serine and diacylphosphatidyl ethanolamine that are currently introduced as negatively charged components in biologically applicable vesicle preparations are reported to induce aggregation of platelets in the body because they are physiologically active. It has been elucidated that administration of the vesicle preparations also causes severe side effects such as thrombocytopenia and dysfunction of white blood cells.
While long chain fatty acids have been used for a simplified method of introducing negative charges on the surface of the vesicle without using any negatively charged phospholipids, single chain fatty acids cannot be stably introduced into the molecular assembly. Instead, there is a problem that a part of the fatty acid leaks into the aqueous phase, or is extracted by lipoproteins and albumin in the blood.
Taking into account the above situations, the object of the invention of the present application is to solve the problems of the prior art, and to provide a negatively charged lipid that can stably add negative charges to the surface of a vesicle without any side effects.